Carpet backing adhesive and method of making

ABSTRACT

THERE IS PROVIDED AN ADHESIVE COMPOSITION FOR BONDING CARPETING YARNS TO THE CARPETING BACKING CONSISTING ESSENTIALLY OF HYDROXY ACRYLIC ACID ESTER LATEX, MELAMINE-FORMALDEHYDE CONDENSATE, DODECENYL SUCCINIC ANYDRIDE AND ZINC OXIDE IN DEFINED PROPORTIONS. A METHOD FOR MAKING THE ADHESIVE COMPOSITON, AND ITS USE, ARE ALSO PROVIDED.

United States Patent CARPET BACKING ADHESIVE AND METHOD OF MAKING Erich F. Kujas, Philadelphia, Pa., assignor to Prodesco, Inc., Perkasie, Pa. No Drawing. Filed Oct. 6, 1969, Ser. No. 864,205 Int. Cl. C08g 37/32 US. Cl. 26029.4 UA 10 Claims ABSTRACT OF THE DISCLOSURE There is provided an adhesive composition for bonding carpeting yarns to the carpeting backing consisting essentially of hydroxy acrylic acid ester latex, melamine-formaldehyde condensate, dodecenyl succinic anhydride and zinc oxide in defined proportions. A method for making the adhesive composition, and its use, are also provided.

BACKGROUND OF l HE INVENTION In the manufacture of tufted carpeting, yarns of textile fibrous materials, which may be of natural origin such as wool, mohair, cotton, and the like, or synthetic, such as polyamide (nylon) viscose rayon, polyesters, polyacrylonitrile, and the like, are Pushed through a fabric backing which may be a non-woven fabric or a woven fabric, like burlap or cotton. An adhesive is applied to the loops of the yarns which are flush with the back side or ultimate bottom of the carpeting to bond them to the backing. A secondary backing, which may be woven, such as burlap or cotton scrim, or non-woven may then be placed over the loops and primary backing. If the secondary backing is suificiently open, the adhesive may be applied after this is placed, otherwise the secondary backing is placed over the wet adhesive which has already been applied to the primary backing and yarn loops. The yarns at the front or ultimate top side of the carpeting are frequently cut. The primary function of the adhesive is to bond the tufted yarns in place, with a secondary function to hold the secondary backing, if used, in place.

The adhesives heretofore available for the aforesaid purposes generally have been based on a natural or synthetic latex (see, for example, Pat. No. 2,748,446). Pat. No. 3,215,647 relates to a foamed latex composition, which may contain an acrylic latex and a coreacting melamine-formaldehyde condensate, stated to be useful as a rug backing.

The compositions available heretofore as carpet backing adhesives have possessed many limitations. In the first place, they do not wet and penetrate the backing and yarns satisfactorily to provide a firm, stable bond. Subsequent cleaning, which involves the use of water and detergents, causes rapid deterioration of the limited bond resulting in the yarns (including individual plies in a multiply yarn), or individual fibers or filaments thereof, being easily pulled out of the backing. This is particularly severe with yarns of fibrous materials, like mohair, nylon, polyesters, acrylics, and the like, which do not have scaled surfaces or which are not crimped. Piece dyeing of carpeting made with such adhesives, involving hot or boiling aqueous dye solutions, also causes rapid deterioration of the limited bond. And the prior adhesive compositions, even after curing, often contain components which leach out into the dye bath with deleterious results, such as causing unlevel dyeing, particularly with certain synthetic yarns. More over, these adhesives often do not cure well or rapidly at elevated temperatures, coagulating to tacky accumulations and requiring one or two additional passes through the curing oven and even standing overnight to complete the "ice cure. Other limitations, such as poor shelf life in the container, relatively rapid surface hardening (skinning) on exposure to air and poor flexibility after curing, have been noted with adhesives heretofore available.

It is the principal object of the present invention to provide an improved carpet backing adhesive. 7

It is another object of the present invention to provide a method for making the improved carpet backing adhesive.

It is a further object of the present invention to provide an improvement in the manufacture of carpeting through the use of the improved adhesive of the present invention.

These and other objects will become apparent from a consideration of the following specification and claims.

The novel adhesive composition of the present invention consists essentially of a hydroxy acrylic acid ester latex, melamine-formaldehyde condensate, dodecenyl suc cinic anhydride and zinc oxide, the stated components being present in the following relative proportions, by weight: the hydroxy acrylic acid ester latex, about parts of acrylic latex solids; the melamine-formaldehyde condensate, about 2 parts; the dodecenyl succinic anhydride, about 2 parts; and the zinc oxide, about 12 parts. The composition has a pH of from about 6.1 to about 6.8. Preferably, calcium hydroxide, and/ or magnesium hydroxide, in an amount of about 1 part on the stated basis, is included as a filler.

The adhesive composition is preferably prepared as follows: The melamine-formaldehyde condensate and the dodecenyl succinic anhydride are first mixed at a temperature of from about to about F. The resulting mixture is then mixed with the hydroxy acrylic acid ester latex at a temperature of from about 100 to about F. To the resulting mixture is then mixed the zinc oxide (dry), and, at about the same time, the calcium and/or magnesium hydroxide, if used, at a temperature of from about 100 to about F. The final mixture is at from about 100 to about 140 F. to provide complete blending. The composition may then be cooled to room temperature and stored for ultimate use or it may be used immediately.

One of the principal components of the present adhesive composition is a hydroxy acrylic latex. This is essentially a high solids content (about 50%) emulsion of a poly hydroxyacrylic (including methacrylic) acid ester. The preferred material is a poly hydroxyalkylmethacrylate in which the alkyl group contains 2 to 3 carbon atoms, namely poly hydroxyethylmethacrylate and poly hydroxylpropylmethacrylate and mixtures thereof, especially poly hydroxyethylmethacrylate.

The second important component of the present adhesive is the melamine-formaldehyde condensate. The preferred material in this regard is essentially methylol melamine formed by condensing one mol of formaldehyde with one mol of melamine. The melamine-formaldehyde condensate is believed to react with the hydroxyacrylic acid ester polymer causing crosslinking on curing.

However, the advantageous characteristics of the present adhesive depend upon the inclusion of the dodecenyl succinic anhydride and the zinc oxide in the stated proportions. The former, which is a liquid compatible with the other components, provides functional groups enhancing cross-linking of the acrylic latex on curing, imparting flexibility, high temperature resistance and detergent and water resistance to the cured adhesive. In addition, the dodecenyl succinic anhydride alters the viscosity of the composition causing it better to wet and penetrate yarns and backing evenly, without bleeding out of the top side of the backing, and imparts long shelf life to the adhesive. The zinc oxide stabilizes the composition, including its viscosity as a function of the compositions pH of from about 6.1 to about 6.8, and serves as a curing promoter.

The inclusion of calcium hydroxide and/or magnesium hydroxide is particularly advantageous as a filler to control and adjust the pH of the composition and hence its viscosity. Calcium hydroxide is preferred.

The following is a specific example of the adhesive composition of the present invention and its preparation: with 2.5 parts, by weight, of melamine-formaldehyde condensate, essentially methylol melamine (in the form of a high viscosity liquid containing 80% solids and providing 2 parts of melamine-formaldehyde condensate solids) are mixed 2 parts, by weight, of dodecenyl succinic anhydride, at 120 F. The resulting mixture is then added to and mixed with 180 parts, by weight, of hydroxy acrylic latex (essentially poly hydroxyethylmethacrylate, 50% solids, providing 90 parts, by weight, of solids), at 125 F. There are then added 12 parts, by weight, of zinc oxide (oven dried) and 1 part of calcium hydroxide, and the total is heated, While mixing, at 140 F. The resulting adhesive has a pH of about 6.2. Poly hydroxypropylmethacrylate latex may be used to replace some or all of the poly hydroxyethylmethacrylate.

The adhesive composition of the present invention has an excellent shelf life, having stood in a closed container for 3 months without any apparent change. Moreover, it has been cooled in a refrigerator without the deleterious results often noted with other latex compositions. When applied to yarn loops and adjacent backing, it readily wets them penetrating into the yarns and the backing Without, however, bleeding through deleteriously to the front or ultimate top side of the carpeting. On heating to from about 215 to about 300 F. for curing, the adhesive cures completely and evenly in 1-2 minutes depending upon the temperature. Curing the adhesive at elevated temperatures does not result in discoloration thereof (staining) as has been found to be the case with most other latex adhesives. Carpeting made using the present adhesive can be, in the cured or partially cured condition, subjected to piece dyeing (the heat encountered during piece dyeing and setting being relied upon to complete the cure, if necessary) without weakening the bond, causing deterioration of the adhesive or loss of fiber into the dye bath. Moreover, the composition is compatible with other aspects of carpet manufacture; for example, nothing leaches from the adhesive into the piece dye bath to contaminate the latter. The cured adhesive is flexible and resilient and is not adversely afiected by detergent solutions commonly used in cleaning (shampooing) carpeting. It has also been found to be fire resistant according to AATCC test methods 33-1962 and 34-1966. The cured adhesive has a high degree of porosity and exhibits good affinity for dyestuffs normally used in piece dyeing carpeting; hence very little or no adhesive can be seen as such after piece dyeing, depending upon the particular dyestuif and yarn. Tufted carpeting made of smooth fibers, utilizing the present adhesive, has been subjected to piece dyeing and to cleaning with detergent solutions, and the yarns and individual fibers thereof have remained locked in place by the adhesive bond.

While the present adhesive composition has been described largely in terms of its utility as a backing adhesive for tufted carpeting, it will be realized that the adhesive may also be used with other types of carpeting wherein it is desired adhesively to bond yarns to backing.

What is claimed is:

1. An adhesive composition for bonding carpeting yarns to carpet backing consisting essentially of a hydroxy acrylic acid ester latex, a melamine-formaldehyde condensate, dodecenyl succinic anhydride and zinc oxide, said components being present in the following relative proportions, by weight: said hydroxy acrylic latex, about parts of acrylic latex solids; said melamine-formaldehyde condensate, about 2 parts; said dodecenyl succinic anhydride, about 2 parts; and said zinc oxide about 12 parts, and the composition having a pH of from about 6.1 to about 6.8.

2. The composition of claim 1 containing also about 1 part of calcium hydroxide and/or magnesium hydroxide on the stated basis.

3. The composition of claim 1 wherein said hydroxy acrylic acid ester latex is essentially a poly hydroxylalkylmethacrylate latex in which the alkyl group contains 2 to 3 carbon atoms.

4. The composition of claim 3 wherein said hydroxy acrylic latex is essentially poly hydroxyethylmethacrylate.

5. The composition of claim 1 wherein said melamineformaldehyde condensate is essentially methylol melamine.

6. The composition of claim 3 wherein said melamineformaldehyde condensate is essentially methylol melamine.

7. The composition of claim 4 wherein said melamineformaldehyde condensate is essentially methylol melamine.

8. The composition of claim 6 containing also about 1 part of calcium hydroxide and/or magnesium hydroxide on the stated basis.

9. The method of making an adhesive composition suitable for bonding carpeting yarns to carpet backing which comprises mixing dodecenyl succinic anhydride with a melamine-formaldehyde condensate at a temperature of from about to about F.; mixing the resulting mixture with a hydroxy acrylic acid ester latex at a temperature of from about 100 to about F., and subsequently mixing zinc oxide with the resulting mixture at a temperature of from about 100 to about F.

10. The method of claim 9 wherein about 1 part of calcium hydroxide and/or magnesium hydroxide is mixed with said mixture when said zinc oxide is mixed therewith.

References Cited UNITED STATES PATENTS 3,007,836 11/1961 McNamara ct al. 161-67 U 3,215,647 11/1965- Dunn 260-296 H U 3,390,035 6/1968 Sands 161-67 X 3,486,920 12/1969 Sington 161-67 X 3,505,156 4/1970 Handscomb et al. 161-67 OTHER REFERENCES The Condensed Chemical Dictionary, sixth edition,

Reinhold Publishing Co., 1965, p. 416.

Handbook of Adhesive by Skirt, Reinhold Publishing Co., 1962, pp. 280-281.

JULIUS -F ROME, Primary Examiner I. B. LOWE, Assistant Examiner US. Cl. X.R. 

